The name of RSR Fitter, who has died aged 92, shouts from the bookshelves of hundreds of thousands of wildlife enthusiasts, on the spines of identification guides that helped and inspired generations of naturalists. Throughout his life, Richard was active in working for wildlife conservation.

As early as 1934, while on a birdwatching trip to Lundy Island, Richard considered writing a book to help people identify wild birds. But it was not until after the second world war, when, by chance, he bumped into the talented young birdwatcher and artist Richard Richardson, that he could take the idea forward. The result was the Collins Pocket Guide to British Birds (1952), illustrated by Richardson, a quirky but invaluable publication with a user-friendly system grouping birds according to habitat, size and colour - rather than the scientific order that most books use. Richard felt that many guides were written for people who already knew which bird was which; his book was intended to help beginners, and it succeeded admirably.

A second Collins pocket guide, in 1956, in collaboration with David McClintock, dealt with wild flowers, and is still used by many amateur enthusiasts. Up to a few weeks before his death, Richard was still revising Finding Wild Flowers (1972), again to help the enthusiast get more from the hobby. He was also embarking on his autobiography.

Richard was born in London: his first memory was of sitting in a pram, watching ducks on the pond at Tooting Bec. Shortly afterwards, a glimpse of a song thrush's nest with eggs set him on an inevitable course. He developed his knowledge of birds while at Eastbourne College, and became involved in London's natural history while studying at the London School of Economics, making contact with other wildlife enthusiasts, such as Max Nicholson. After taking an economics degree in 1933, he became interested in social sciences and worked at the Institute for Political and Economic Planning till the outbreak of the second world war, when he joined RAF Coastal Command.

After the war, he became secretary of the wildlife conservation committee of the Ministry of Town and Country Planning, dealing mostly with new nature reserves. His first book, London's Natural History (1945), was the third in the Collins New Naturalist series. Further books followed, and he became assistant editor of the monthly magazine, the Countryman.

He became a director of the Council for Nature, served on the councils of the RSPB and the British Trust for Ornithology, founded the Berkshire, Buckinghamshire and Oxfordshire Naturalists' Trust (now the wildlife trust, BBOWT), helped found the British Deer Society, and, in 1975, was involved in an early inquiry into badgers and TB.

Richard was, at various times, on the steering committee, chairman and member of honour of the International Union for the Conservation of Nature (now the World Conservation Union), and was closely involved with the Fauna and Flora Preservation Society (now Fauna and Flora International) and the ICBP (now BirdLife International).

On a visit to America on the mid-1960s, he found a new bird book, The Golden Guide, that placed short texts directly opposite pictures, and urged Collins to do something similar. With illustrator Herman Heinzel and bird distribution expert John Parslow, a new guide, The Birds of Britain and Europe, with Africa and the Middle East - pop-ularly known as "Heinzel, Fitter and Parslow" - was published in 1972. A recent revision keeps it near the top of the list. Richard's wife, Maisie, whom he married in 1938, was a hard-working collaborator on his researches.

As recently as May 2002, Richard co-wrote a paper in the journal Science with his son Alistair, a biology professor at York University, on the effects of climate change as shown by the changing flowering periods of wild flowers. As an observer and recorder of facts, he was able to show such changes from personal records, kept over 50 years, mostly in the Chilterns, where he lived. Books with Alistair and the artist Marjorie Blamey included Wild Flowers of Britain and Ireland (1974) and several Collins flower guides.

Richard was a popular, funny and inspiring speaker, still visiting schools and working on three books just months before he died. Maisie died in 1996. He is survived by his two sons and a daughter.

Stephen Moss writes: Having learned my birding with the help of Richard Fitter's books, I was privileged that our paths crossed twice in his later years, when he was as active as ever.

The first time was sitting in his garden in the Chilterns, when I interviewed him for my book on the social history of birdwatching, A Bird in the Bush. He and Max Nicholson were the last surviving links with the years before the second world war, when birdwatching was done at a more leisurely pace and participants had time to stop and admire other forms of wildlife. With typical modesty, Richard underplayed his part in the postwar birdwatching boom, and lamented the fact that today's dawn chorus pales into insignificance compared to that of his childhood.

Earlier this year, he took part in the BBC2 series Springwatch, talking about his decades of keeping records of signs of spring. We filmed Richard sitting in a woodland glade, with his tattered notebooks spreads out before him; he seemed amused that the data within them had proved to be so important. The UK Phenology network, with its thousands of participants, is a fitting tribute to him, and to a lifetime devoted to the observation, study and enjoyment of nature.

· Richard Sidney Richmond Fitter, naturalist and writer, born March 1 1913; died September 3 2005